Numerous methods and apparatus for electrophotography, electrostatic recording and electrostatic printing are known in the art. Typically, a charged photosensitive surface, for example a charged photosensitive drum, is irradiated with an optical image and an electrostatic latent image is formed on the photosensitive surface. In the development process, a developing agent, i.e., toner, is adhered to the electrostatic latent image.
Typically, toner is fed to a developer roller by a metering blade positioned against the surface of the developing roller. The developer roller, with the toner on its surface, is typically rotated in a direction opposite to that of the photosensitive drum, and toner adheres to the electrostatic latent image to develop the image. Various toner compositions have been developed in order to provide improved copying, recording and/or printing with such apparatus.
Some printers include what is commonly referred to as an "accumulator roller," an unheated aluminum idler running against a back-up roller. The accumulator roller idles against the backup roller, and the function of the accumulator roller is to remove toner from the backup roller thereby preventing paper jams. Toner transferring from the fuser roller to the back-up roller transfers and sticks to the cooler, higher surface energy accumulator roller rather than immediately transferring back to the prints. However, as toner builds up on the accumulator roller, large pieces of toner may occasionally transfer back to the back-up roller and then to the prints, causing print quality to become objectionable. Further, continual buildup of toner on the accumulator roller may eventually cause the fuser to fail mechanically.
Grushkin et al., U.S. Pat. No. 4,810,610, disclose cold pressure fixable toner compositions comprising a blend of resin particles and magnetite particles. Grushkin et al. teach that the toner compositions may contain carbon black. Grushkin et al. further teach that resin particles include suitable thermoplastics such as polyolefins, polyamides, copolymers of ethylene and vinyl acetate and mixtures thereof, and that polyolefins include polyethylene, polypropylene or copolymers of ethylene and propylene.
Grushkin et al., U.S. Pat. No. 4,877,707 disclose a pressure fixable toner composition comprised of resin particles selected from the group consisting of ethylene/propylene copolymers, ethylene-co-vinyl acetate polymers, polyamides, and mixtures thereof, magnetite, and a release fluid. Grushkin et al. further teach the toner contains conductive particles on the surface.
Sakashita, U.S. Pat. No. 5,051,331, discloses a toner comprising a binding resin, a low-molecular weight olefin copolymer. Sakashita teaches the low-molecular weight olefin copolymer has at least two olefin monomer repeating units and has two or more peaks of melting at temperatures at between 90.degree. C. and 170.degree. C.
Tanikawa et al., U.S. Pat. No. 5,364,722, disclose a toner comprising a binder resin and a hydrocarbon wax, and heat-fixing methods using the toner. Tanikawa et al. teach that the binder resin may be composed of homopolymers of styrene and derivatives thereof, and styrene copolymers, such as styrene-acrylate copolymer. Tanikawa et al. further teach the hydrocarbon wax provides a differential scanner calorimeter curve showing an onset temperature of heat of absorption in the range of 50.degree. to 110.degree. C., and at least one heat absorption peak in the range of 70.degree.-130.degree. C.
Hagiwara et al., U.S. Pat. No. 5,389,484, disclose a toner having a binding resin having an acid component with an acid value of from 0.5 mg KOH/g to 100 mg KOH/g, a colorant, and defined aromatic amines. Hagiwara et al. teach that the acid component of the resin interacts with the amino group of the aromatic compounds to form an amide bond, thereby cross-linking the polymer chains. Hagiwara et al. further teach that this can impart a rubber elasticity to the toner, so that its anti-offset properties can be improved.
Suzuki et al., U.S. Pat. No. 5,538,828, disclose a toner resin composition comprising a binder primarily composed of vinyl copolymer and an ethylene copolymer. Suzuki et al. further teach the ethylene copolymer is prepared by copolymerizing ethylene and at least one alpha- or beta-derivative of acrylic acid or an unsaturated dicarbonic acid derivative. Suzuki et al. further teach toner-separating agents such as a low molecular weight polyester or polypropylene wax may be added.
Taguchi et al., U.S. Pat. No. 5,466,555, disclose a releasing composition for a toner comprising a low molecular weight polypropylene and at least one modified polyolefin. Taguchi et al. teach that suitable polypropylenes include polypropylene homopolymers, and copolymers of polypropylene with one or more other monomers copolymerizable therewith, for example, ethylenes and olefins. The releasing composition may be used in toners which comprise the releasing agent, colorant, and binder resin. Taguchi et al. teach suitable binder resins include styrenic and/or acrylic resins.
Sawai et al., U.S. Pat. No. 5,565,294, disclose a toner containing a colorant, a binding resin, and a polyethylene having a melt viscosity of 22000 to 26800 mPa.multidot.s at 140.degree. C. Sawai et al. teach that when the melt viscosity of polyethylene is less than 2200 mPa.multidot.s at 140.degree. C., toner components are not evenly dispersed at a kneading step in the production process of the toner.
Inoue et al., U.S. Pat. No. 5,658,999, disclose production of propylene waxes by polymerizing propylene with a solid catalyst formed of a transition metal compound or a reaction product between the transition metal compound and an organometallic compound, an aluminoxane and a fine particulate carrier. Inoue et al. further disclose a toner composition composed essentially of a binder resin, a colorant, and as a releasing agent, a propylene wax.
Akimoto et al., U.S. Pat. No. 5,707,772, disclose a toner comprised of a resin, a colorant, and a releasing agent. Akimoto et al. teach the releasing agent is a low molecular weight polyolefin polymer synthesized using a metallocene catalyst. Akimoto et al. further teach the number average molecular weight of the polyolefin is from 2,000 to 10,000, and the ratio of weight average molecular weight to number average molecular weight (Mw/Mn) is 1.6 to 3.5.
Osterhoudt et al., U.S. Pat. No. 5,811,214, disclose a developer comprising negatively charged toner particles comprising a polymeric binder, magnetic material, and a charge control agent wherein the toner particle surface contains particles of cerium dioxide, dimethyldichlorosilane treated silica, and dimethylsiloxane treated silica. Osterhoudt et al. teach the polymeric binder may comprise styrene and an alkyl acrylate and/or methacrylate. Osterhoudt et al. further teach that useful additives include release agents such as waxes, including copolymers of ethylene and propylene having a molecular weight of 1,000 to 5,000 g/mole.
Kawaji et al., U.S. Pat. No. 5,908,727, disclose a binder obtained by mixing a starting material monomer mixture of two different polymerization reactions, a compound which can react with both of the starting monomers, and a releasing agent.
Eguchi et al., U.S. Pat. No. 5,928,825, disclose a toner comprising a binder resin, a colorant, and a lubricant. Eguchi et al. teach the lubricant comprises a modified polyethylene wax obtained by grafting a monomer selected from the group consisting of styrene and unsaturated carboxylic acid onto an ethylene homo- or copolymer.
Hashimoto et al., U.S. Pat. No. 5,948,584, disclose a toner comprising toner particles containing at least a binder resin, a colorant and a wax. Hashimoto et al. teach that the binder resin comprises a hybrid component comprising a vinyl polymer component and a unit of polyester component bonded to each other.
Kuwashima et al., U.S. Pat. No. 5,952,138, disclose a magnetic developer comprising a magnetic toner containing at least a binder resin, a magnetic material, and a hydrocarbon wax which is synthesized by reaction of carbon monoxide with hydrogen or by polymerizing ethylene and which has a number average molecular weight of from 600 to 1,000. Kuwashima et al. teach the wax should have an acid value of less than 2.0 mg KOH/g, and that if the acid value is higher than 2.0 mg KOH/g, the wax's interfacial adhesion to the binder resin may become so large that smearing of characters results.
Urashima, et al., U.S. Pat. No. 5,955,233, disclose a toner comprising a polymer obtained by suspension polymerization in an aqueous medium of a polymerizable monomer composition, a coloring agent, and optionally, a magnetic powder in the presence of an epoxy resin and a crystalline (meth)acrylic ester type polymer. Urashima et al. further teach an offset-preventing agent may be incorporated, and that suitable offset-preventing agents include polyolefin wax which has a weight average molecular weight in the approximate range of 1,000 to 45,000, preferably 2,000 to 6,000, such as homopolymers of polyethylene, polypropylene and polybutylene, or olefin copolymers such as ethylene-propylene copolymer.
Unfortunately, many prior art toner compositions accumulate excessively on the accumulator roller and may be shed from the roller, thereby decreasing print quality and/or causing mechanical failure of the printer. Accordingly, a need exists to develop toners which will not accumulate excessively on the accumulator roller and which maintains good print quality.